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Tiny songbirds caught during their annual migration and shipped 3000 kilometres away can still find their way to nesting grounds, a US study shows.

Princeton University researchers trapped 30 white-crowned sparrows as they migrated from breeding grounds in Alaska to winter nesting sites in the southwestern US and Mexico.

The birds were flown in the windowless pet compartments of commercial jets from the west coast city of Seattle, Washington to New Jersey, 3700 kilometres away on the east coast.

A few days later the birds were released with a tiny radio transmitter attached to a piece of cotton glued between their shoulders.

Their flight paths were followed by researchers on the ground and in a small plane.

A very simple pattern emerged: the 15 adult birds realised they needed to fly southwest to get to their nesting grounds while the 15 juveniles, who had never made the trip before, simply continued to fly south.

Scientists have long been puzzled how migratory birds are able to find nesting sites thousands of kilometres away even when they do not have other birds to guide them.

The white-crowned sparrow typically flies alone and at night as it makes its long journey and the ability of juveniles to find the winter nesting grounds on their own indicates an innate orientation.

Nesting grounds

The fact the adults were able to correct their route after a 3700 kilometre diversion suggests the birds may also build a navigational map as they migrate, the authors say in the study published in the latest Proceedings of the National Academy of Sciences.

"On the basis of one migratory journey from Alaska to southwest North America, white-crowned sparrows obtain information that allows them to reach their wintering grounds from an area that their normal migratory route does not encompass," says lead author Dr Kasper Thorup of the Zoological Museum, University of Copenhagen.

"And allows them to correct for vast displacements very rapidly, within days, at least, hinting that migratory birds may possess a global navigational map."

While researchers have tracked birds using bands on their legs, including those shipped far away from their typical migratory routes, this is the first study in which researchers tracked displaced birds as they flew.